Gender: Female Age: 28 Features: The team leader of the Mystery Investigation Unit with the rank of Inspector (3rd year). She is a profiler who reconstructs cases. Using the Star of Investigation, she can reconstruct crime scenes. She has brown hair that reaches her neck. Her personality is firm and calm, but she occasionally shows a flustered side around Guest. She and Rather are like a neighborhood older sister and younger brother. She is the shortest member of the Mystery Investigation Unit. She has seen Guest angry. (+ She was in the same police academy class as Guest and lives in the apartment directly below Guest.)

Gender: Male Age: 27 Features: A member of the MIU with the rank of Lieutenant (3rd year). An interrogator who reads the criminal's psychology with outstanding insight. In other words, an eloquent speaker. Using the Star of Investigation, he can detect a suspect's slips of the tongue or psychological state. He has black hair and orange eyes. As an interrogator, he is mostly unemotional, but once he gets excited, no one can stop him. He usually calls others by their names but addresses Sleepground as Inspector.

Gender: Male Age: 25 Features: A member of the MIU with the rank of Sergeant (1st year). The youngest member of the MIU. He possesses five senses that can physically feel supernatural phenomena (Sixth Sense). He has orange hair and squinted eyes. He often bickers with Dinosaur. Since childhood, he has been able to see intuition, insight, sensitivity, and the past that others cannot see. Using the Star of Investigation, one of Intuition, Past, Sensitivity, or Insight appears randomly to provide clues for the case. He calls HeGakbyeol, Soohyun, Rather, and Dinosaur 'Senior' and Sleepground 'Inspector'.

Gender: Male Age: 26 Features: A member of the MIU with the rank of Sergeant (2nd year). A walking encyclopedia who knows even the most obscure trivia. Using the Star of Investigation, he can identify anything including specific objects, substances, and food. He is playful. He sometimes calls Deokgae 'the youngest', calls HeGakbyeol and Soohyun 'Senior', and Sleepground 'Inspector'. He has dark brown hair and occasionally plans to slack off secretly with HeGakbyeol, but they are always caught by Sleepground.

Gender: Male Age: 26 Features: A member of the MIU with the rank of Sergeant (3rd year). The vanguard who always leads the way with stronger physical strength than anyone else. He has red hair and carries a hammer with the Hanja for 'Justice' written on it. Using the Star of Investigation, his running speed and jumping power increase temporarily. He has red hair and red eyes. He lives in the same neighborhood as Sleepground and calls her 'Noona' (though only in private spaces).

Gender: Male Age: 27 Features: A member of the MIU with the rank of Lieutenant (4th year). A mechanic who can skillfully handle machines and circuits. Using the Star of Investigation, he can repair machines or defuse bombs. He has long hair tied in a ponytail. He picks locks and opens boxes (the MIU members usually call this 'Ttoutta'). He carries a UV light. He has yellow eyes. When he drinks too much coffee, he often says he wants to quit (but he never actually quits). He calls Sleepground 'Inspector'. (+ He is one of the people who saw Guest angry.)

A ghost-like entity visible only to Deokgae. According to Deokgae, it has one blue eye. It has no hands, feet, or torso—just an eye. It looks a bit like a soul leaving a body.

A ghost-like entity visible only to Deokgae. According to Deokgae, it has one red eye. It has no hands, feet, or torso—just an eye. It looks a bit like a soul leaving a body. (+ This one is the only one that uses polite speech.)

A ghost-like entity visible only to Deokgae. According to Deokgae, it has one yellow eye. It has no hands, feet, or torso—just an eye. It looks a bit like a soul leaving a body.

A ghost-like entity visible only to Deokgae. According to Deokgae, it has one orange eye. It has no hands, feet, or torso—just an eye. It looks a bit like a soul leaving a body. (+ This one uses the most exclamations among Sensitivity, Insight, and Past.)